9.7
1. Comparison of footprints inside a canopy between Large Eddy Simulation and Lagrangian models
T. V. Prabha, Univ. of Georgia, Griffin, GA; and M. Y. Leclerc and D. Baldocchi
The flux footprint associated with in-canopy sources deserves considerable attention due to the inhomogeneous and spatially heterogeneous nature of turbulence inside the canopy. The Large eddy simulation (LES) and the Lagrangian simulation are used in this study to quantify canopy footprints. The simulations with LES are carried out for multiple release of passive tracers inside the canopy at three vertical locations ( 0.05h, 0.35h and 0.75h, where h is canopy height ) from line sources along cross wind direction. The LES model is initialized with flow fields from an earlier simulation for the same canopy. The LES runs are performed for a period of 80 min and stable statistics are derived for a forest canopy. Initial 30 min are excluded from the analysis to avoid interference from non-equilibrium of concentration fields. Results are presented for 30 min averaging period and relevance of longer averaging time for in-canopy flux footprint are also discussed. Present simulations indicate a single peak for flux footprints for all three releases and are located close to the tracer source. The majority of footprint fluxes are confined within the canopy except for the tracer at 0.75 h. The downwind distribution of flux footprint associated with the source close to canopy bottom is confined to 2 h. Concentration and flux footprints are compared with similar simulations from a Lagrangian model.
Session 9, Turbulence and Dispersion in Canopies Part 2
Thursday, 23 May 2002, 1:30 PM-4:00 PM
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